The present invention relates to solid-state image pickup apparatus and fabricating method thereof having a solid-state image pickup device chip packaged in CSP (chip size package), and more particularly relates to the construction and fabricating method of hermetic seal thereof.
In recent years, there has been an advancement in size reduction for example mainly of portable equipment and, as a result, a further downsizing is demanded also of the casing and inner circuit board therefor. Of those parts to be mounted on a circuit board, semiconductor devices are not excepted from such demands for downsized equipment, and their reduction in size is also required. The same can be said about solid-state image pickup devices which are among the semiconductor devices.
A packaging system as shown in FIG. 1 has generally been used for solid-state image pickup apparatus. In particular, a solid-state image pickup device chip 101 is die-bonded to a package 102 for example of ceramics and a bonding wire 103 is used to achieve predetermined electrical connections between the solid-state image pickup device chip 101 and package 102. The solid-state image pickup apparatus is then constructed by using a step portion 104 formed at an edge of package 102 to adhere a glass lid 105 thereto to achieve a hermetic seal with providing a space over the surface of the solid-state image pickup device chip 101. It should be noted that numeral 106 in FIG. 1 denotes an external lead.
In solid-state image pickup apparatus having such construction, use of package 102 and glass lid 105 for hermetically sealing the entire solid-state image pickup device chip resulted in an increased packaging size and thus had been difficult to be applied to the fields where smaller package size was required.
To eliminate such disadvantage, the present applicant had proposed solid-state image pickup apparatus constructed as disclosed in Japanese patent laid-open application Hei-7-202152. A sectional view of such solid-state image pickup apparatus is shown in FIGS. 2 and 3. In FIG. 2, only the light-receiving area on the solid-state image pickup device chip 101 is hermetically sealed by means of a sealing member which includes a flat-plate portion 107 made of a transparent member and a frame portion 108 integrally formed therewith at a side portion of a lower surface thereof. Glass, quartz, sapphire, transparent resin or the like is used as the transparent member for constituting the flat-plate portion 107. In the solid-state image pickup apparatus shown in FIG. 3, on the other hand, instead of integrally forming a hermetic seal portion, a flat-plate portion 109 and a frame portion 110 are adhered to each other to constitute the hermetic seal portion. Here frame portion 110 may be constituted by such inorganic materials as ceramics, glass, silicon or such metal as Kovar or 42-alloy. Further, it is also possible that an epoxy, phenol, or silicone resin may be printed or pattern-formed by photolithography on the surface of the solid-state image pickup device chip 101 to form the frame portion 110.
By constructing solid-state image pickup apparatus in this manner, a smaller size packaging thereof is possible and, especially in a solid-state image pickup apparatus having a micro-lens, the solid-state image pickup apparatus can be achieved without degrading the light converging capability of the micro-lens even when such optical components as a filter, lens, prism, etc., is adhered to the surface of the hermetic seal portion. Further, fabrication method has also become simpler, since hermetic seal portions can be formed at once for all of a large number of solid-state image pickup device chips in a wafer.
The previously proposed solid-state image pickup apparatus as described above, however, has the following problems to be solved. First, the structure of the integrally formed, hermetic seal portion as shown in FIG. 2 requires an integral forming of the hermetic seal portion having a flat-plate portion and a frame portion by using such transparent material as glass. Precision in processing is thus required and difficulties such as an increased amount of work in fabrication are foreseen.
Further, the method of constructing the hermetic seal portion by adhering flat-plate portion and frame portion to each other as shown in FIG. 3, especially the method of constructing the frame portion by means of a pattern forming of resin, requires the processing steps of forming a resinous pattern, i.e., application of the resin onto a wafer, printing or photolithography, developing and etching. There is thus a problem that the number of processing steps is increased.
Furthermore, a more serious problem presumably occurs with this technique when the solid-state image pickup apparatus has a micro-lens. This is because a micro-lens, usually, is formed also from a resin. For example, after applying a resin over the entire surface of a wafer, the processing steps of patterning and etching of the frame portion must be performed before the resin cures. If etching is performed before the curing of the resin, however, the resin capable of becoming the frame portion is also etched away similarly as the portion of resin to be removed and there is a possibility that a sufficient frame is not formed. If etched after the curing of the resin, on the other hand, though a desired shape for the frame is formed, there is a possibility that the micro-lens is etched away at the same time of the etching of the unnecessary portion of resin to be removed due to the fact that the micro-lens is also made of a resin.
Moreover, in those previously proposed including the packaging system as shown in FIG. 1, wire bonding must be performed to connect the I/O pad of a solid-state image pickup device chip and the electrodes of the package. An increased number of I/O terminals in the solid-state image pickup device chip results in an increase in the processing time of wire bonding for the I/O pad (terminals) and affects the throughput.
As the above, those previously proposed are with various problems in the construction of hermetic seal portion, even though smaller size packaging is possible and hermetic seal portions can be formed at once for all chips in the form of a wafer.